As the sensitivity of analytical techniques continues to improve, it is increasingly desirable to carry out chemical and biochemical reactions and/or analyses using very small volumes of samples and reagents. This is especially true in situations involving expensive substances. Accordingly, it is now popular to utilize very small volumes of such substances laid down as microdroplets on the surface of, or inside, a well or substrate, such as a slide, micro-card, chip or membrane.
Not only is it often desirable to transfer ultra-small volumes of individual samples and reagents in the form of droplets, it is becoming increasingly popular to arrange numerous such microdroplets in close proximity to one another in the form of an array on a substrate. High-density array formats, or microarrays, permit many reactions to be carried out in a highly parallel fashion, saving space, time and money.
Multi-channel micropipette devices are available for laying down several reagent microdroplets at once. Devices of this type typically have 8 or 12 micropipettes, fixed side-by-side in a linear array. Generally, these devices are unsuitable for quickly producing very dense arrays, since only a few microdroplets (usually 8 or 12) can be laid down at a time with such devices. Furthermore, these micropipette devices are typically not capable of dispensing femtoliter volumes of samples. Thus, the production of very dense arrays, e.g., having hundreds or thousands of microdroplets tends to be a very tedious and time-consuming process.
In view of the above, the need is apparent for an apparatus and method useful for dispensing a micro-volume of a substance onto a substrate in a quick and efficient manner. Preferably, the apparatus should be relatively easy to use and readily adaptable. The present invention is designed to meet these needs.